Because I finally do, though it is not a SaaS. At my current workplace, DarwinApps, we've spent two years to finally narrow it down. First, we've tried Pivotal Tracker, then some other services I can't even remember, then Asana for more than a year. We have multiple projects running at once and the most obvious flaw of these is the lack of meaningful task numbering. In a voice meeting, we must navigate to the tracker, search and paste full URL of an issue, which is really painful. Can you remember any of the following URLs ?:
Then we've reached Jira, what a relief ! The links are finally usable / easy to remember and construct:
And Jira is definitely the best one SaaS, at least for our needs, as it has meaningful task numbering and multiple dimensions to assign tickets to. However, in the end, we've sticked to Redmine, but that's really another story, which I can only tell if you are ready to maintain your own virtual / dedicated server. What I really wonder what SaaS are you using for issue tracking, and whether you are happy with it, and if not - what is the reason ? Please leave a note in the comments, thank you !